Audio Codec Quality Shootout

There are literally dozens of audio codecs out there now, but only a few are relevant to the average consumer. Our audio quality comparisons will focus on the four most popular formats: MP3, AAC, WMA, and Ogg Vorbis:

MP3:

By far the most ubiquitous format for compressed digital audio, MP3 needs little introduction. Though distributing encoders and decoders requires a license, there are scores of free players and encoders available. There’s quite a range of quality amongst the different encoders, so we used what we felt was the best-sounding one you can get. LAME isn’t technically an encoder (it has to be compiled into one) but a quick Google search will turn up plenty of already-compiled versions. They can be combined with free CD rippers like Exact Audio Copy to produce an all-in-one ripping package. LAME is considerably slower than other MP3 encoders, but produces the best audio quality. The LAME build we used was 3.95.1.

Windows Media Audio 9

Another familiar codec, this one is built into the latest Windows Media Player (among other applications) and offers a wealth of features. The standard stereo version is most common, but there are versions that offer 24bit/96KHz sound at up to 5.1 channels, and even a version that offers mathematically lossless compression. Our tests focused on the common stereo version, but we threw in a Lossless track just to see if listeners could pick it out. We used the free Windows Media Encoder to encode our test clips.

AAC

AAC has been around for a long time as part of the MPEG-2 spec, but has been updated for better low-bitrate quality in the MPEG-4 spec. It wasn’t very popular among home users until the explosive popularity of Apple’s iTunes application, which defaults to AAC encoding for ripping CDs. As it is by far the most popular home AAC encoding application now, we used iTunes to encode our AAC test files. Not many portable players support AAC, but the iPod does, and it’s the current market leader.

Ogg Vorbis

Ogg Vorbis is similar to MP3 or AAC compression formats, but with one important difference: It’s completely free, unpatented, and open-source. Its royalty-free nature has made it popular with some game developers and software publishers — it’s used in several top PC games including Unreal Tournament 2003, Serious Sam: The Second Encounter, and Harry Potter and the Chamber of Secrets. You can find out more about Ogg Vorbis and download the source or tools from Vorbis.com. Only a handful of portable players support .ogg files, but many are capable of it and, since it’s free, vendors can add support if their user base demands it.

It’s not enough to simply test the four most popular compressed audio formats, though. There’s always the matter of what bitrate to choose. We tested each clip at three common bitrates: 64k per second (useful for smaller flash memory-based devices), 128k (for larger flash memory devices or small hard drive based players), and a quality-based variable bitrate setting with the quality up to 98% (for large hard drive based players or storage on your PC). The exception here is AAC. Though true variable bitrate support is possible in the AAC standard, the most popular AAC encoder, iTunes, only offers constant bitrate options at this time. Therefore, our AAC tests did not include the VBR setting.

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